Definition of cryptozoon in US English:

cryptozoon

(also cryptozoön)

noun

Geology
  • A supposed reef-forming fossil of Cambrian or Precambrian age having a laminated, discoid structure and subsequently shown to be the remains of colonies of cyanobacteria (stromatolites). Also (in form Cryptozoon) as a genus name.

Origin

Late 19th century. From crypto- + -zoon, after scientific Latin Cryptozoön, genus name.